Human corneal dystrophies and degenerations which have been clinically documented are studied as keratoplasty specimens with histochemical stains, scanning and transmission electron microscopy, and immunologic techniques in an attempt to elucidate pathogenetic mechanisms. This approach has provided insight into cell-to-cell relationships in the normal and diseased states. In patients with primary and recurrent macular corneal dystrophy, intercellular and extracellular accumulation of fibrillogranular material was observed in the corneal stroma, Descemet's membrane, and corneal endothelium. The presence and production of collagen, glycoconjugates, and collagenase have been investigated with immunofluorescent, electrophoretic, and chromatographic methods. Electron microscopic studies performed on keratoconus and pellucid degeneration. Keratoplasty specimens from granular corneal dystrophy and controls were examined by combinations of immunohistological stains, transmission electron microscopy, and SDS gel electrophoresis.